Print PDF
Favorite
Email
Step 8Follow and Test the Bad Trace.
Yes. We already spotted where we think the problem is, but we could be wrong! Note that each ribbon connector lead to opposite matrix sheets. There's an unprinted sheet between them with holes at each key position. Turn the sheet so the suspect connector is on top.
Note that the three sheets are attached together. DO NOT SEPARATE THEM! We can pull them apart where they aren't melted together, but if we break the bond(s) they will never align properly again.
Follow the trace from the ribbon connector that we noted from the Encoder test. It should eventually lead to one of the offending keys. Actually it will lead to all of them, but we're satisfied when we come to the first one with the problem.
In this case, that line also led to the Asterisk (*), Plus, Minus and Enter keys on the Numeric Keypad before leading to the offending Space key. Since we had no problem with the aforementioned keys, we can assume the problem is in the trace somewhere between the Enter and Space keys.
The previously noted discoloration happens to be right on this trace! So we know just where to test.
Using our Ohm Meter, measure the resistance between two previous known good key points. In this case, it reads about 5 ohms. Now measure from the last known good key point to the first bad key point In our case, this reads about 85K ohms. Yep! The trace is bad!
Use a cotton swab dipped in clean water and lightly clean the bad area. Let it dry completely.
Remeasure the trace from before the bad spot to after the bad spot. Here we read about 76 K ohms. This needs repair!
Note that the three sheets are attached together. DO NOT SEPARATE THEM! We can pull them apart where they aren't melted together, but if we break the bond(s) they will never align properly again.
Follow the trace from the ribbon connector that we noted from the Encoder test. It should eventually lead to one of the offending keys. Actually it will lead to all of them, but we're satisfied when we come to the first one with the problem.
In this case, that line also led to the Asterisk (*), Plus, Minus and Enter keys on the Numeric Keypad before leading to the offending Space key. Since we had no problem with the aforementioned keys, we can assume the problem is in the trace somewhere between the Enter and Space keys.
The previously noted discoloration happens to be right on this trace! So we know just where to test.
Using our Ohm Meter, measure the resistance between two previous known good key points. In this case, it reads about 5 ohms. Now measure from the last known good key point to the first bad key point In our case, this reads about 85K ohms. Yep! The trace is bad!
Use a cotton swab dipped in clean water and lightly clean the bad area. Let it dry completely.
Remeasure the trace from before the bad spot to after the bad spot. Here we read about 76 K ohms. This needs repair!
| « Previous Step | Download PDFView All Steps | Next Step » |
 |
Add Comment
|
